Method of recovering hydrocarbons



21, 1943. H, R, LEGATSK, ET 2,331,254

METHOD OF RECOVERING HYDROCARBONS Filed Aug. 2, 1940 HHGUOSHO in i DENUDED ABSORBENT INVENTOR HAROLD R. LEGATSKI WILL SWERDLOFF Patented Dec. 21, 1943 UNITED STATES PATENT OFFICE 2,331,254 IHETHOD F BEOOVEBING HYDBOCARBONS Harold R. Legatski, Will Swerdloii, and Gerald W.

McCullough, Bartlesvllle, Okla asslgnors to Phillips Petroleum Company. a corporation of Delaware Application August 2, 1940, Serial No. 349,590

2 Claims. (01. 196-8) This invention relates to an improved method for recovering all but the most volatile fraction of hydrocarbon gases.

This invention is a continuation-impart of the co-pending application, Serial No. 181,053,flled December 21, 1937, which application issued as they are compressed and sent through pipe 33 to the desorber i3. The flashing oil of gases and vapors in the vent and surge tank 24 and in the vent tank 30 efiects partial denudation of the absorbent. Partly denuded absorbent from the vent tank 30 is divided intotwo streams, one passing through the control valve 34, the pump 35, the cooler 36 and the pipe l8 to the absorber; and the other passing through the float controlled valve 31 and the heater 38 to the third vent tank 39. Vapors from the vent tank 39 are withdrawn 1 through the back pressure regulator 40, coma rough separation of the components according to volatility. V

With reference to the drawing, the figure is a diagrammatic elevation view of a system embodying the present invention.

Referring to the drawing, a main absorber is designated by the numeral ;l and supplemental absorbers by the numerals l and 13. These absorbers may be any suitable contacting devices, preferably bubble plate columns, in which a stream of gas may be borught into intimate countercurrent contact with a stream of liquid. To distinguish between these absorbers, the terminology used hereinafter shall be, absorber, designated by numeral ll; *reabsorber, designated by numeral l2; and desorber, designated by numeral i3, Gas to be processed is admitted to the base of theabsorber ll through the pipe i4 and residue gas leaves the to'p of the absorber through the back pressure regulator l5 and the pipe l6. Pipes l1, l8, and I9 are connected to the absorber ii for the admission of absorbent, pipes l8 and I9 having branches for admitting the oil at various points in the absorber. Rich absorbent leaves the base of the absorber through the fioat controlled valve 20. The stream of rich absorbent is divided, part flowing through the pipe 2| to the top of the desorber l3 and part flowing through the pipe 22 and heater 23 to the vent and surge tank 24. The vapor from the vent tank 24 is passed by a back pressure regulator 25 to a, compressor 26 which compresses the vapors and pumps them through the cooler 21 to the base of the reabsorber i2. Liquid from the vent tank 24 as controlled by a rate-of-flow controller 28 is passed through the heater 29 to a second vent tank 30. Vapors from the vapor space of the vent tank 30 pass through the back pressure regulator 3| to the compressor 32 where pressed by the compressor 4|, cooled in the cooler 42 and passed to the product accumulator 43.

'Partly denuded absorbent, having a greater degree of denudation than that from the vent tank 30 is withdrawn from the vent tank 39 through the float controlled valve 44 and the cooler 45 to the pump 46 from which it is pumped through the pipe l9 into the absorber I I.

The rich absorbent entering the top of the desorber l3 through the pipe 2i is countercurrently contacted with gases entering the base of the desorber. Desorber l3 accomplishes substantially complete removal of methane from the absorbent stream. The demethanized rich absorbent from the base ofthe desorber as controlled by the float controlled valve 41 is sent through the heater 48 to a conventional still 49 ior stripping or denudation. Such a still isi;., well...known in the art and may be provided withthe necessary auxiliary equipment, not shown in the drawing. Hydrocarbon vapors from the still are cooled and condensed by the cooler 50 and are conducted to the product accumulator 43 by the pipe 5i. In the product accumulator 43 the condensate, comprising the heavy hydrocarbon components, is separated from the uncondensed vapors and gases. The condensate passes the float controlled valve 52 and passes to storage as product A through the pipe 53.

Uncondensed vapors and gases leave the product accumulator 43 through the back pressure regulator 54. Part of the gases and vapors may be passed through the control valve 55 and pipe 56 to the base of the desorber; the remainder is compressed and cooled, by compressor 51 and cooler 58, and passed to a second product ac- In the product accumulator 59v valve 60 and passed to storage through the pipe 6|. Gases from the product accumulator are passed through the control valve 82 into the pipe base .of the reabsorber 12 through the-valve 6'6.

Denuded absorbent from the still 49 is pumped by the pump 61 through the cooler 88 and the I cooled denuded absorbent is admitted to the top of the reabsorberTi through the valve 89 and to the top of the absorber l I through the pipe l1 and the valve HI, Residue gas from the top of the reabsorber passes the back pressure regulator II and passes out of the system through the pipe 12.

. ,The rich absorbent from the base of the reabsorber is passed by the float controlled valve 13 through the pipe 14 to the desorber It for demethanization. sorbent from the absorber and reabsorber, enter- In the .desorber, the rich abing the desorber through pipes and H respectively, are stripped oi methane and other undesirable gases by the action of thevarious gas streams entering the lower part of the desorber- The gases are fed to the desorber at various points depending upon their methane contents. Gas having the lowest methane content is fed to the bottom of the desorber, and the other gases are fed at various points above the bottom in the order of their increasing methane content. Gases from the top of the desorber are passed by .the back pressure regulator 15 through the line 16 to the intake of the compressor 26. From the compressor 26 they are passed, with gases from the vent'and surge tank 24, throughthe cooler 21 and into the base or the reabsorber l2.

As shown in the drawing, the absorber II is operated with a stream of denuded absorbent fed to its top, and with partly denuded absorbent fedto the absorber atappropriate points below thetop plate. Partly denuded absorbent from the vent tanks may be supplied to the absorber through pipe I8, pipe l9 or through both. In order that no valuable constituents may be lost in the outlet gas by stripping of the partially denuded absorbent, the stream of denuded absorbent is introduced at the top of the absorber ll. Below the point of entry of the partly denuded absorbent, the absorbent streams combine to give an effect of high absorbent rate in the bottom section of the absorber.

The advantage of this absorption system over conventional absorption systems is that this system increases'the amount of desirable hydrocarbons removed from the gas by circulating more absorption oil or lower molecular weight hydrocarbon liquid without increasing steam or heating v k requirements. Product is recovered from the additional amount of absorption oil by flashing ,the rich oil invent tanks.

We claim: 1. The process of treating hydrocarbon gas comprising countercurrently contacting a stream of the gas with a plurality of absorbents in an absorption zone having initial and final points with respect to the gas stream, withdrawing the rich absorbent from the absorption zone, passing a part of the rich absorbent to aseries of ebuliition to said initial and final points, recycling liquid effluent of a succeeding ebullition zone to the absorber at a point between said intermediate and said final points, and recycling denuded absorbent from the distillation zone to the absorber at said final point.

2. The process. of treating hydrocarbon gas comprising countercurrently contacting a stream of the gas with a plurality of absorbents in an absorption zone having initial and final points of contact with respect to the gas stream, withdrawing the rich absorbent from the absorption zone, passing a part of the rich absorbent to a series of ebullition zones wherein ebullition of said rich absorbent takes place to effect partial denudation of the rich absorbent, returning liquid efiluent of one ebullition zone to the absorption zone at an intermediate point in relation to said initial and final points, returning liquid efiiuent of a succeeding ebullition zone to the absorber at a point between said intermediate and said final point, passing vaporous eflluent of the ebullition zones to a reabsorption zone, to recover desirable gases evolved in the ebullition zones, contacting the vapors in the reabsorption zone with denuded absorbent, passing liquid efiluent of the reabsorption zone to a desorption zone to remove undesirable absorbed gases therefrom by displacement with desirable gases, passing a part of the rich absorbent from said absorption zone to said desorption zone, contacting the rich absorbent in the desorption zone with a stream of light hydrocarbon vapors, passing liquid eiiluent of the desorption zone to-a distillation zone, to release absorbed hydrocarbons therefrom; pass- 7 ing liquid efliuent of the distillation zoncto the absorptionzone at said final point, and passing liquid efiluent of the distillation zone to the reabsorption zone as said denuded absorbent.

, HAROLD R. LEGATSKI. WILL SWERDLOFF. GERALD W, McCULLOUGH. 

